The present invention relates to a friction vacuum pump comprising a fixed element bearing rows of stator blades and a rotating element bearing rows of rotor blades whereby the rows of stator blades and rotor blades are arranged concentrically with respect to the axis of rotation of the rotating element and engage with each other.
Turbomolecular vacuum pumps are a kind of friction pump, see for example U.S. Pat. No. 5,577,883. They are designed just like a turbine with rows of rotor and stator blades. Stator and rotor are substantially cylindrical in shape and are arranged coaxially with respect to the rotational axis of the rotating component. The longitudinal axes of the stator and rotor blades which engage in alternating fashion, extend radially so that a substantially axial direction for the pumping action results. One or several pairs of a row of rotor blades and a row of stator blades form a pump stage. The pumping properties (pumping capacity, compression) of a pump stage are adjusted through the design of the blades, preferably through their angle of incidence.
In the instance of turbomolecular vacuum pumps according to the state-of-the-art, there exists a minimum requirement for the number of pump stages, which can not be reduced any further. Thus turbomolecular vacuum pumps according to the state-of-the-art have to be relatively long, in particular since the drive motor contributes further to the axial length. Moreover, in the instance of the known turbomolecular vacuum pumps only one component—commonly the rotor—can be made of a single piece, whereas the other component—commonly the stator—needs consist of a multitude of components in order to be able to assemble the engaging rows of stator blades.
It is the task of the present invention to create a turbomolecular vacuum pump of the aforementioned kind which is significantly shorter in the axial direction.
This task is solved by the present invention through characterising features of the patent claims.